Abstract
A rectangular pulse vertical field circuit of transistor type was devised and assembled as a substitute for usual crowbar type. The circuit is composed of 10 units, each consisting of a capacitor, a transistor and a comparator. The current rise time, the maximum field and the current duration of the circuit are 750A/ms, 18G and 2.5ms, respectively. When the pulse vertical field of the circuit having a short current fall time is applied on a plasma, the horizontal displacement of the plasma is reduced, the plasma is stably confined around the center of a vacuum vessel and the duration of plasma current is elongated. The rapidly rising pulse vertical field can clarify the effect of the vacuum vessel as a thin-casing shell.
